Handle lectures that require custom credentials
Adds the required logic to handle lecture videos that use their own credentials to log in such as Introduction to Machine Learning.
Removes support for passing a login-token as login with username and password is faster and simpler.
Append the difference between lecture title and video title to the output filename of videos to handle cases such as where a lecture uploads two videos on the same day but one of them is titled
<Lecture name> - Tutorial.
This should fix all issues that prevent correct downloading of videos from Introduction to Machine Learning.